In the old photos of the matches that Alvin York took part in, you will see more than one match rifle with a 3/4 stock. This was the other option used to get a flat base to rest the barrel on. Many full stocked match rifles had a flat area three quarters of the way up the forearm, to get a steady rest.
My opinion is that a regular rifle might have been rebarreled with a heavier, and longer, match barrel, which accounted for the odd stock length.
Hungry Horse